From the description of the injuries , it would appear that this is not a simple ' Whiplash ' injury .
Medical evidence , will have to be commisioned , to support your claim for injuries , sustained , and any report must be done by an expert , complying with the
( CPR ) Civil Procedure rules - Personal Injury protocols - before a compensator will usually make any offers of settlement .
Therefore I would not suggest you try and deal with the claim yourself ; but instead seek professional assistance .
As been said above , try and instruct a firm of solicitor (s) who have a specialist Personal Injury Team .
There is no reason why you should not get all of the compensation agreed by the compensator plus reasonable costs, paid - if the solicitor states that they wiil be taking a 'cut' of the compensation , then walk away and find another firm .
As for the amount of compensation you will get - this depends ( amongst other things ) on the nature of the injuries sustained and the prognosis for recovery - and to a large extent on how robust your solicitor is , in pursuing your claim
Given that he was a passenger , he will have no difficulty on the liability side as he is an ' innocent ' party - his claim will either be dealt with by the insurers of the taxi , or the insurers of the other vehicle .